The invention relates to a device for a safety interlocking in protection equipment for preventing reaching into spaces which are dangerous, in particular in accordance with dangerous movements or in current conducting equipment in housings, whereby the given protection equipment is in a protective position during the dangerous operating condition and is locked; however, it can be opened during the non-dangerous operating condition.
In machines with movements which are dangerous, current conducting housings, for example, switchboards, are subject to strict legal regulations, so as to protect human beings operating the same. The safety technical requirements for such safety interlocking devices are compiled in the DIN-prestandard 31.001. Therein, exemplified solutions are stated, whereby the following goal of protection is obtained. As long as the protection device is not in its protective position, the dangerous operating condition should not be switched on.
In all previously known solutions as well as in the commercially available embodiments one starts from the principle to make the dangerous movement safe by means of electrical switches. They may be designed as a circuit opener or a circuit closer. Until now, two different embodiments has been known in addition to exclusively electrical safety devices. The one embodiment represents an interlocking under a current. The protection device, for example, a protective hood or a sliding door is interlocked by means of a bolt or a slide which is actuated by a magnet and is kept under current in the locking position. The other embodiment represents an interlocking device operated by means of a spring pressure. Thereby, a locking bolt or a slide is brought into the interlocking position by means of a spring and is held in that position by the spring pressure. The opening is performed by a magnet which is dimensioned such that is sufficiently overcomes the force of the spring. Both embodiments behave different during a power failure. In the first mentioned embodiment with an interlocking under current, the interlocking device automatically opens due to the power failure, because the magnet is pushed back into its initial position by its return spring. The protective hood, or the door can then be opened. If due to power failure the magnet is pushed back and the door opens too rapidly accidents cannot be excluded during a rash. In order to prevent such accidents, an additional time delay, preferably of the mechanical type, would be required, which naturally would result in a considerable structural expenditure, without assuring a real reliability. In the second known embodiment, namely the interlocking by means of a spring pressure, the opening by the magnet during power failure is not possible. One has to manually push back the spring in any kind of a skillfull manner, so as to enable the opening of the protective hood or the door. However, this would also be possible during the dangerous movement. Thus, the protection device would be ineffective.